Coupling For Rods

ABSTRACT

A cold worked and spinodally-hardened copper alloy comprising from about 8 to about 20 wt % nickel, and from about 5 to about 11 wt % tin, the remaining balance being copper, and having a 0.2% offset yield strength of at least 75 ksi, is used to form a sucker rod coupling or subcoupling. Each coupling is formed from a core having two ends, each end having an internal thread. These box ends engage the pin of a sucker rod or other rod. The exterior surface of the core includes grooves running between the two ends.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/633,593, filed Feb. 27, 2015, now U.S. Pat. No. ______, which claimspriority to U.S. Provisional Patent Application Ser. No. 62/008,324,filed Jun. 5, 2014, and U.S. Provisional Patent Application Ser. No.62/065,275, filed Oct. 17, 2014. The content of the above applicationsare incorporated by reference in their entirety.

BACKGROUND

The present disclosure relates to couplings made from aspinodally-hardened copper alloy. The couplings are particularly usefulfor connecting sucker rods to affect a connection between a power sourceand a pump, and may also be useful for other couplings used in the oiland gas industry, such as a polished rod coupling or a subcoupling.

Hydrocarbon extraction apparatuses typically include a pump forextracting hydrocarbons from an underground reservoir, a power sourcefor providing power to the pump, and a sucker rod lift system connectingthe power source and the pump. The sucker rod lift system includes aseries of sucker rods that are joined together by couplings. The suckerrods and couplings are joined by a pin-and-box threaded connection.Damage to threaded connections due to galling (wear due to adhesionbetween sliding surfaces) can compromise the mechanical integrity of thejoint and lead to failure of the connection between the power source andthe pump. In addition, the sucker rod lift system operates within aconduit. Damage to the conduit caused by repetitive contact between theouter surface of the coupling and the inner surface of the conduit cancompromise the mechanical integrity of the conduit, leading to leakageof the hydrocarbons carried by the conduit into the environment. Suchleakage effectively stops the pumping process and often leads to verycostly additional operations to remediate such failures.

Desired characteristics of sucker rod couplings and similar couplingsinclude high tensile strength, high fatigue strength, high fracturetoughness, galling resistance, and corrosion resistance. Conventionalcouplings are typically comprised of steel or nickel alloys which lackthe full complement of preferred intrinsic characteristics, particularlygalling resistance. Expensive surface treatments are typically used toincrease galling resistance on couplings made from steel or nickelalloys, as well as on the inside of the conduit inside which thecoupling is disposed. These surface treatments eventually wear off, andmust be re-applied periodically over the course of the lifetime of theparts in order to be effective.

It would be desirable to develop new sucker rod couplings havingimproved intrinsic galling resistance as well as other desirableproperties.

BRIEF DESCRIPTION

The present disclosure relates to couplings made fromspinodally-hardened copper alloys, and more specifically sucker rodcouplings. The couplings have a unique combination of propertiesincluding high tensile strength, high fatigue strength, high fracturetoughness, galling resistance, and corrosion resistance. Thiscombination of properties delays the occurrence of destructive damage tothe couplings and other components in pump systems using such couplings(e.g., sucker rods and conduits), while providing mechanicalfunctionality during hydrocarbon recovery operations. This also extendsthe useful service life of such components, significantly reducing thecosts of equipment used to recover hydrocarbons. Some couplings of thisdisclosure are especially shaped to include at least one groove on theirexterior surface, so that fluid flow is not impeded.

Disclosed herein in various embodiments are couplings for a sucker rod,comprising a spinodally-hardened copper-nickel-tin alloy comprising fromabout 8 to about 20 wt % nickel, and from about 5 to about 11 wt % tin,the remaining balance being copper, wherein the alloy has a 0.2% offsetyield strength of at least 75 ksi. The coupling is formed from a corehaving a first end and a second end, each end containing an internalthread. An exterior surface of the core includes at least one grooverunning from the first end to the second end.

The copper-nickel-tin alloy can comprise, in more specific embodiments,about 14.5 wt % to about 15.5 wt % nickel, and about 7.5 wt % to about8.5% tin, the remaining balance being copper. The alloy may have a 0.2%offset yield strength of at least 85 ksi, or at least 90 ksi, or atleast 95 ksi.

In particular embodiments, the alloy of the coupling can have a 0.2%offset yield strength of at least 95 ksi and a Charpy V-notch impactenergy of at least 22 ft-lbs at room temperature. Alternatively, thealloy of the coupling can have a 0.2% offset yield strength of at least102 ksi and a Charpy V-notch impact energy of at least 12 ft-lbs at roomtemperature. Alternatively, the coupling can have a 0.2% offset yieldstrength of at least 120 ksi and a Charpy V-notch impact energy of atleast 12 ft-lbs at room temperature.

The internal threads on the first end and the second end of the couplingcan have the same box thread size. Alternatively, for a subcoupling, theinternal threads on the first end and the second end can have differentbox thread sizes.

Sometimes, a bore runs through the core from the first end to the secondend, the internal threads of each end being located within the bore.Each end of the coupling can also include a counterbore at an endsurface.

The internal threads can be formed by roll forming. The internal threadsof the coupling may have a Rockwell C hardness (HRC) of about 20 toabout 40. The coupling can be formed by cold working and spinodalhardening.

In some embodiments of the coupling, the at least one groove runsparallel to a longitudinal axis extending from the first end to thesecond end. In other embodiments, the at least one groove runs spirallyfrom the first end to the second end, or in other words curls around theexterior surface. The groove(s) can have an arcuate cross-section or aquadrilateral cross-section

In particular embodiments, the first end and the second end of thecoupling are tapered downwards (i.e. the diameter at each end is lessthan the diameter in the middle of the coupling). For example, the endscan be tapered linearly or parabolically.

Also disclosed herein are rod strings, comprising: a first rod and asecond rod, each rod including an end having a pin with an externalthread; and a coupling having a structure as described above and herein.The internal thread of the first end of the coupling is complementarywith the external thread of the first rod, and the internal thread ofthe second end of the coupling is complementary with the external threadof the second rod. Again, the coupling comprises a spinodally-hardenedcopper-nickel-tin alloy comprising from about 8 to about 20 wt % nickel,and from about 5 to about 11 wt % tin, the remaining balance beingcopper, wherein the alloy has a 0.2% offset yield strength of at least75 ksi.

Also disclosed herein are pump systems comprising: a downhole pump; apower source for powering the downhole pump; and a rod string locatedbetween the downhole pump and the power source; wherein the rod stringcomprises: a first rod and a second rod, each rod including an endhaving a pin with an external thread; and a coupling as describedherein.

Also disclosed herein in various embodiments are couplings for a suckerrod, comprising a spinodally-hardened copper-nickel-tin alloy comprisingfrom about 8 to about 20 wt % nickel, and from about 5 to about 11 wt %tin, the remaining balance being copper, wherein the alloy has a 0.2%offset yield strength of at least 75 ksi.

The copper-nickel-tin alloy can comprise, in more specific embodiments,about 14.5 wt % to about 15.5 wt % nickel, and about 7.5 wt % to about8.5% tin, the remaining balance being copper. The alloy may have a 0.2%offset yield strength of at least 85 ksi, or at least 90 ksi, or atleast 95 ksi.

In particular embodiments, the alloy of the coupling can have a 0.2%offset yield strength of at least 95 ksi and a Charpy V-notch impactenergy of at least 22 ft-lbs at room temperature. Alternatively, thealloy of the coupling can have a 0.2% offset yield strength of at least102 ksi and a Charpy V-notch impact energy of at least 12 ft-lbs at roomtemperature. Alternatively, the coupling can have a 0.2% offset yieldstrength of at least 120 ksi and a Charpy V-notch impact energy of atleast 12 ft-lbs at room temperature.

The coupling may include a core having a first end and a second end,each end containing an internal thread. The internal threads on thefirst end and the second end can have the same box thread size.Alternatively, for a subcoupling, the internal threads on the first endand the second end can have different box thread sizes.

Sometimes, a bore runs through the core from the first end to the secondend, the internal threads of each end being located within the bore.Each end of the coupling can also include a counterbore at an endsurface.

The internal threads can be formed by roll forming. The internal threadsof the coupling may have a Rockwell C hardness (HRC) of about 20 toabout 40. The coupling can be formed by cold working and spinodalhardening.

Also disclosed herein are rod strings, comprising: a first rod and asecond rod, each rod including an end having a pin with an externalthread; and a coupling including a core having a first end and a secondend, each end containing an internal thread; wherein the internal threadof the first end of the coupling is complementary with the externalthread of the first rod, and the internal thread of the second end ofthe coupling is complementary with the external thread of the secondrod; and wherein the coupling comprises a spinodally-hardenedcopper-nickel-tin alloy comprising from about 8 to about 20 wt % nickel,and from about 5 to about 11 wt % tin, the remaining balance beingcopper, wherein the alloy has a 0.2% offset yield strength of at least75 ksi.

Also disclosed herein are pump systems comprising: a downhole pump; apower source for powering the downhole pump; and a rod string locatedbetween the downhole pump and the power source; wherein the rod stringcomprises: a first rod and a second rod, each rod including an endhaving a pin with an external thread; and a coupling including a corehaving a first end and a second end, each end containing an internalthread; wherein the internal thread of the first end of the coupling iscomplementary with the external thread of the first rod, and theinternal thread of the second end of the coupling is complementary withthe external thread of the second rod; and wherein the couplingcomprises a spinodally-hardened copper-nickel-tin alloy comprising fromabout 8 to about 20 wt % nickel, and from about 5 to about 11 wt % tin,the remaining balance being copper, wherein the alloy has a 0.2% offsetyield strength of at least 75 ksi.

These and other non-limiting characteristics of the disclosure are moreparticularly disclosed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a brief description of the drawings, which arepresented for the purposes of illustrating the exemplary embodimentsdisclosed herein and not for the purposes of limiting the same.

FIG. 1 is a schematic illustration of an embodiment of a pumping systemof the present disclosure.

FIG. 2 is a cross-sectional view showing the engagement of a sucker rodcoupling with two sucker rods.

FIG. 3A is a cross-sectional view showing the interior of a sucker rodcoupling.

FIG. 3B is a cross-sectional view showing the interior of a subcoupling.

FIG. 4 is a plan view (i.e. looking down the longitudinal axis) of anexemplary sucker rod coupling of the present disclosure, having fourgrooves on the exterior surface of the core. The grooves have an arcuatecross-section.

FIG. 5 is a side exterior view of the coupling taken along plane AA ofFIG. 4. The grooves run parallel to a longitudinal axis extendingbetween the two ends of the coupling. The ends of the coupling arelinearly tapered.

FIG. 6 is a side cross-sectional view of the coupling taken along planeBB of FIG. 4. This coupling includes a counterbore and internal threads.

FIG. 7 is a side exterior view of another coupling taken along plane AAof FIG. 4. This coupling has the same plan view, but the exterior viewis different. Here, the ends of the coupling are parabolically tapered.

FIG. 8 is a plan view of another sucker rod coupling of the presentdisclosure, having four grooves on the exterior surface of the core. Thegrooves have a spiral or helical cross-section.

FIG. 9 is a side exterior view of the coupling taken along plane CC ofFIG. 8. The grooves have a spiral cross-section, i.e. are angledrelative to the longitudinal axis extending between the two ends of thecoupling. The ends of the coupling are linearly tapered.

FIG. 10 is a plan view of another sucker rod coupling of the presentdisclosure, having six grooves on the exterior surface of the core. Thegrooves have a quadrilateral cross-section.

FIG. 11 is a picture of one end of a sucker rod coupling made from acopper alloy according to the present disclosure.

FIG. 12 is a picture showing the measured hardness across an internalthread of a coupling made from a copper alloy according to the presentdisclosure (50×).

FIG. 13 is a micrograph at 50× magnification showing the grain structureof the entire thread.

FIG. 14 is a micrograph at 100× magnification showing the grainstructure of the tip of the thread.

FIG. 15 is a micrograph at 100× magnification showing the grainstructure at the center of the thread.

FIG. 16 is a micrograph at 100× magnification showing the grainstructure at the thread root.

FIG. 17 is a micrograph at 200× magnification showing the grainstructure at the side of the thread.

DETAILED DESCRIPTION

A more complete understanding of the components, processes andapparatuses disclosed herein can be obtained by reference to theaccompanying drawings. These figures are merely schematicrepresentations based on convenience and the ease of demonstrating thepresent disclosure, and are, therefore, not intended to indicaterelative size and dimensions of the devices or components thereof and/orto define or limit the scope of the exemplary embodiments.

Although specific terms are used in the following description for thesake of clarity, these terms are intended to refer only to theparticular structure of the embodiments selected for illustration in thedrawings, and are not intended to define or limit the scope of thedisclosure. In the drawings and the following description below, it isto be understood that like numeric designations refer to components oflike function.

The singular forms “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise.

As used in the specification and in the claims, the term “comprising”may include the embodiments “consisting of” and “consisting essentiallyof.” The terms “comprise(s),” “include(s),” “having,” “has,” “can,”“contain(s),” and variants thereof, as used herein, are intended to beopen-ended transitional phrases, terms, or words that require thepresence of the named components/steps and permit the presence of othercomponents/steps. However, such description should be construed as alsodescribing compositions or processes as “consisting of” and “consistingessentially of” the enumerated components/steps, which allows thepresence of only the named components/steps, along with any impuritiesthat might result therefrom, and excludes other components/steps.

Numerical values in the specification and claims of this applicationshould be understood to include numerical values which are the same whenreduced to the same number of significant figures and numerical valueswhich differ from the stated value by less than the experimental errorof conventional measurement technique of the type described in thepresent application to determine the value.

All ranges disclosed herein are inclusive of the recited endpoint andindependently combinable (for example, the range of “from 2 grams to 10grams” is inclusive of the endpoints, 2 grams and 10 grams, and all theintermediate values).

The term “about” can be used to include any numerical value that canvary without changing the basic function of that value. When used with arange, “about” also discloses the range defined by the absolute valuesof the two endpoints, e.g. “about 2 to about 4” also discloses the range“from 2 to 4.” The term “about” may refer to plus or minus 10% of theindicated number.

The present disclosure relates to couplings that are made from aspinodally strengthened copper-based alloy. The copper alloys of thepresent disclosure may be copper-nickel-tin alloys that have acombination of strength, ductility, high strain rate fracture toughness,and galling protection. More particularly, the couplings arecontemplated to be artificial lift couplings, sucker rod couplings, orsubcouplings used in the oil and gas industry, particularly forhydrocarbon recovery systems.

FIG. 1 illustrates the various parts of a pump system 100. The system100 has a walking beam 122 that reciprocates a rod string 124 thatincludes a polished rod portion 125. The rod string 124 is suspendedfrom the beam for actuating a downhole pump 126 that is disposed at thebottom of a well 128.

The walking beam 122, in turn, is actuated by a pitman arm which isreciprocated by a crank arm 130 driven by a power source 132 (e.g., anelectric motor) that is coupled to the crank arm 130 through a gearreduction mechanism, such as gearbox 134. The power source may be athree-phase AC induction motor or a synchronous motor, and is used todrive the pumping unit. The gearbox 134 converts motor torque to a lowspeed but high torque output for driving the crank arm 130. The crankarm 130 is provided with a counterweight 136 that serves to balance therod string 124 suspended from the beam 122. Counterbalance can also beprovided by an air cylinder such as those found on air-balanced units.Belted pumping units may use a counterweight that runs in the oppositedirection of the rod stroke or an air cylinder for counterbalance.

The downhole pump 126 may be a reciprocating type pump having a plunger138 attached to the end of the rod string 124 and a pump barrel 140which is attached to the end of tubing in the well 128. The plunger 138includes a traveling valve 142 and a standing valve 144 positioned atthe bottom of the barrel 140. On the up stroke of the pump, thetraveling valve 142 closes and lifts fluid, such as oil and/or water,above the plunger 138 to the top of the well and the standing valve 144opens and allows additional fluid from the reservoir to flow into thepump barrel 140. On the down stroke, the traveling valve 142 opens andthe standing valve 144 closes in preparation of the next cycle. Theoperation of the pump 126 is controlled so that the fluid levelmaintained in the pump barrel 140 is sufficient to maintain the lowerend of the rod string 124 in the fluid over its entire stroke. The rodstring 124 is surrounded by a conduit 111 which in turn is surrounded bya well casing 110. The rod string 124 below the polished rod portion 125is made of sucker rods that are held together via sucker rod couplings123.

FIG. 2 is a side view illustrating the engagement between two suckerrods 210, 220 and a sucker rod coupling. Each sucker rod 210, 220includes a rod body 212, 222 and two rod ends 214, 224 (only one endshown for each rod). The rod end includes an externally-threaded pin (ormale connector) 216, 226; a shoulder 218, 228 adapted to abut the endsurface of the coupling; and a drive head 219, 229 which can be engagedby a tool for torquing and tightening the sucker rods.

The sucker rod coupling 230 itself is a core 232 having a first end 234and a second end 236, each end corresponding to a box and having aninternal thread (i.e. a female connector) 238, 240 for engaging the pinof a sucker rod. The core has a generally cylindrical shape, with thelength being greater than the diameter. Each end has an end surface 235,237 that abuts the shoulder of the sucker rod. As illustrated here, abore 242 runs entirely through the core from the first end 234 to thesecond end 236 along the longitudinal axis of the core. Both internalthreads 238, 240 are located on the surface of the bore, and a dottedline indicates where the two ends meet in the center of the core. Here,both internal threads have the same box thread size, and arecomplementary to the external threads on the sucker rods. The dimensionsof the sucker rods and the various parts of the sucker rod coupling aredefined by API Specification 11B, the 27th edition of which was issuedin May 2010.

FIG. 3A provides a cross-sectional view of a sucker rod coupling 230,FIG. 3B is a cross-sectional view of a subcoupling 250. The sucker rodcoupling 230 of FIG. 3A includes a counterbore 252, 254 at each endsurface 235, 237. Put another way, the internal thread does not run allthe way to the end surface as in FIG. 2. Here, both internal threadshave the same box thread size as indicated by reference numerals 244,246. The longitudinal axis is also indicated by line 260.

The subcoupling 250 in FIG. 3B has the same structure as the sucker rodcoupling, but differs in that the box thread size of the first end 234is different from the box thread size of the second end 236, asindicated by reference numerals 256, 258. The longitudinal axis is alsoindicated by line 260.

In particular embodiments, the sucker rod coupling 230 of FIG. 2 andFIG. 3A, and the subcoupling 250 of FIG. 3B have substantially smoothcurved exterior surfaces 262 and 264, respectively. In other words, theouter diameter remains constant along the length of these couplings suchthat curved exterior surfaces 262 and 264 are uniform. In particularembodiments, the outer diameter of these couplings is not significantlygreater in diameter compared to the outer diameter of the sucker rods.

Additional variations on such couplings are disclosed in FIGS. 4-6. Moreparticularly, the outer diameter of these couplings is greater than theouter diameter of the sucker rods. This prevents the sucker rods fromcontacting the production tubing (i.e. conduit 111 of FIG. 1)surrounding the rod string. FIG. 4 is a plan view. FIG. 5 is an exteriorview taken along plane AA of FIG. 4. FIG. 6 is a cross-sectional viewtaken along plane BB of FIG. 4.

Referring first to FIG. 4, the coupling 430 is formed from a core 432.The cross-section of the core has a generally circular shape, with abore 442 running entirely through the core along the longitudinal axis.The exterior surface 462 of the core has at least one groove. Here, fourgrooves 471, 472, 473, 474 are shown. The core has an inner diameter 425that also corresponds to the diameter of the bore, and the core also hasan outer diameter 427. Each groove has a depth 475, which is measuredrelative to the outer diameter of the core. Each groove may have anydesired depth, and there may be any number of grooves as well, as longas sufficient material remains of the core to support the rods that arejoined to the coupling. In particular embodiments, the ratio of thegroove depth 475 is at most one-half of the difference between the outerdiameter 427 and the inner diameter 425. In particular embodiments,there is a plurality of grooves, and the grooves are generally spacedevenly around the perimeter of the core.

It is contemplated that the coupling desirably contacts any productiontubing instead of the sucker rods doing so, so as to reduce wear on thesucker rods. One means of doing this is to increase the outer diameterof the sucker rod coupling. However, this could impede fluid flow withinthe production tubing. The presence of the grooves provides a path forfluid flow, reducing the cross-sectional area of the coupling andreducing any impedance in fluid flow due to the use of the coupling.

Referring now to the exterior view of FIG. 5, the coupling has a firstend 434 and a second end 436, and a middle 428. The first end 434 andthe second end 436 taper downwards, i.e. the diameter at the middle 428is greater than the diameter at each end of the coupling. The term“taper” here refers only to the diameter decreasing from the middle toeach end, and does not require the change in diameter to occur in anygiven manner. Here in FIG. 5, the ends of the core taper linearly, i.e.in a straight line. Grooves 471 and 472 are visible as well.Longitudinal axis 460 is also drawn for reference (dashed line).

Referring now to the cross-sectional view of FIG. 6, each end of thecoupling 434, 436 corresponds to a box and has an internal thread (i.e.a female connector) 438, 440 for engaging the pin of a sucker rod. Eachend has an end surface 435, 437 that abuts the shoulder of the suckerrod. The bore 442 runs entirely through the core from the first end 434to the second end 436 along the longitudinal axis 460 of the core. Bothinternal threads 438, 440 are located on the surface of the bore. Here,both internal threads have the same box thread size. A counterbore 452,454 is present at each end 434, 436, where the internal thread does notrun all the way to the end surface.

FIG. 7 is another embodiment of a sucker rod coupling. Here, thecoupling 430 has the same plan view as illustrated in FIG. 4, but theends 434, 436 are tapered parabolically instead of linearly. Thetransition from the middle to each end is arcuate, when viewed from theside. Grooves 471 and 472 are still visible.

FIG. 8 and FIG. 9 illustrate another aspect of the present disclosure.FIG. 8 is the plan view, and FIG. 9 is the side view taken along planeCC of FIG. 8. Here, the grooves do not run parallel to the longitudinalaxis 460. Rather, the grooves 471, 472 run spirally from the first end434 to the second end 436, or put another way from one side of theperimeter to the other side of the perimeter, similar to threads on ascrew. The distance along the longitudinal axis that is covered by onecomplete rotation of a groove (also called the lead) can be varied asdesired.

Finally, FIG. 10 illustrates yet another aspect of the presentdisclosure. The cross-section of the groove can vary as desired, againas long as sufficient material remains of the core 430 to support therods that are joined to the coupling. Here in FIG. 10, the groove 471has a quadrilateral cross-section formed from three sides 481, 482, 483(the fourth side is the perimeter of the core indicated by a dottedline). In contrast, the grooves of FIG. 4 have an arcuate cross-section.

Generally, the copper alloy used to form the couplings of the presentdisclosure has been cold worked prior to reheating to affect spinodaldecomposition of the microstructure. Cold working is the process ofmechanically altering the shape or size of the metal by plasticdeformation. This can be done by rolling, drawing, pressing, spinning,extruding or heading of the metal or alloy. When a metal is plasticallydeformed, dislocations of atoms occur within the material. Particularly,the dislocations occur across or within the grains of the metal. Thedislocations over-lap each other and the dislocation density within thematerial increases. The increase in over-lapping dislocations makes themovement of further dislocations more difficult. This increases thehardness and tensile strength of the resulting alloy while generallyreducing the ductility and impact characteristics of the alloy. Coldworking also improves the surface finish of the alloy. Mechanical coldworking is generally performed at a temperature below therecrystallization point of the alloy, and is usually done at roomtemperature.

Spinodal aging/decomposition is a mechanism by which multiple componentscan separate into distinct regions or microstructures with differentchemical compositions and physical properties. In particular, crystalswith bulk composition in the central region of a phase diagram undergoexsolution. Spinodal decomposition at the surfaces of the alloys of thepresent disclosure results in surface hardening.

Spinodal alloy structures are made of homogeneous two phase mixturesthat are produced when the original phases are separated under certaintemperatures and compositions referred to as a miscibility gap that isreached at an elevated temperature. The alloy phases spontaneouslydecompose into other phases in which a crystal structure remains thesame but the atoms within the structure are modified but remain similarin size. Spinodal hardening increases the yield strength of the basemetal and includes a high degree of uniformity of composition andmicrostructure.

Spinodal alloys, in most cases, exhibit an anomaly in their phasediagram called a miscibility gap. Within the relatively narrowtemperature range of the miscibility gap, atomic ordering takes placewithin the existing crystal lattice structure. The resulting two-phasestructure is stable at temperatures significantly below the gap.

The copper-nickel-tin alloy utilized herein generally includes fromabout 9.0 wt % to about 15.5 wt % nickel, and from about 6.0 wt % toabout 9.0 wt % tin, with the remaining balance being copper. This alloycan be hardened and more easily formed into high yield strength productsthat can be used in various industrial and commercial applications. Thishigh performance alloy is designed to provide properties similar tocopper-beryllium alloys.

More particularly, the copper-nickel-tin alloys of the presentdisclosure include from about 9 wt % to about 15 wt % nickel and fromabout 6 wt % to about 9 wt % tin, with the remaining balance beingcopper. In more specific embodiments, the copper-nickel-tin alloysinclude from about 14.5 wt % to about 15.5% nickel, and from about 7.5wt % to about 8.5 wt % tin, with the remaining balance being copper.

Ternary copper-nickel-tin spinodal alloys exhibit a beneficialcombination of properties such as high strength, excellent tribologicalcharacteristics, and high corrosion resistance in seawater and acidenvironments. An increase in the yield strength of the base metal mayresult from spinodal decomposition in the copper-nickel-tin alloys.

The copper alloy may include beryllium, nickel, and/or cobalt. In someembodiments, the copper alloy contains from about 1 to about 5 wt %beryllium and the sum of cobalt and nickel is in the range of from about0.7 to about 6 wt %. In specific embodiments, the alloy includes about 2wt % beryllium and about 0.3 wt % cobalt and nickel. Other copper alloyembodiments can contain a range of beryllium between approximately 5 and7 wt %.

In some embodiments, the copper alloy contains chromium. The chromiummay be present in an amount of less than about 5 wt % of the alloy,including from about 0.5 wt % to about 2.0 wt % or from about 0.6 wt %to about 1.2 wt % of chromium.

In some embodiments, the copper alloy contains silicon. The silicon maybe present in an amount of less than 5 wt %, including from about 1.0 wt% to about 3.0 wt % or from about 1.5 wt % to about 2.5 wt % of silicon.

The alloys of the present disclosure optionally contain small amounts ofadditives (e.g., iron, magnesium, manganese, molybdenum, niobium,tantalum, vanadium, zirconium, and mixtures thereof). The additives maybe present in amounts of up to 1 wt %, suitably up to 0.5 wt %.Furthermore, small amounts of natural impurities may be present. Smallamounts of other additives may be present such as aluminum and zinc. Thepresence of the additional elements may have the effect of furtherincreasing the strength of the resulting alloy.

In some embodiments, some magnesium is added during the formation of theinitial alloy in order to reduce the oxygen content of the alloy.Magnesium oxide is formed which can be removed from the alloy mass.

In particular embodiments, the internal threads of the coupling areformed by roll forming, rather than by cutting. This process appears toelongate the grains on the outer surface of the threads. Rolled threadshave been found to resist stripping because shear failures must takeplace across the grain, rather than with the grain. This cold workingprocess also provides additional strength and fatigue resistance. As aresult, the internal threads may have a Rockwell C hardness (HRC) ofabout 20 to about 40. The HRC can vary throughout the thread, and thisrecitation should not be construed as requiring the entire thread tohave the same HRC. In particular embodiments, the HRC of the thread is aminimum of 22. The outer surface of the thread may have an HRC of atleast 35.

The alloys used for making the couplings of the present disclosure mayhave a 0.2% offset yield strength of at least 75 ksi, including at least85 ksi, or at least 90 ksi, or at least 95 ksi.

The alloys used for making the couplings of the present disclosure mayhave a combination of 0.2% offset yield strength and room temperatureCharpy V-Notch impact energy as shown below in Table 1. Thesecombinations are unique to the copper alloys of this disclosure. Thetest samples used to make these measurements were orientedlongitudinally. The listed values are minimum values (i.e. at least thevalue listed), and desirably the offset yield strength and CharpyV-Notch impact energy values are higher than the combinations listedhere. Put another way, the alloys have a combination of 0.2% offsetyield strength and room temperature Charpy V-Notch impact energy thatare equal to or greater than the values listed here.

TABLE 1 0.2% Room Preferred Room Offset Ultimate Temperature TemperatureYield Tensile Charpy V-Notch Charpy V-Notch Strength Strength ElongationImpact Energy Impact Energy (ksi) (ksi) at break (%) (ft-lbs) (ft-lbs)120 120 15 12 15 102 120 15 12 20 95 106 18 22 30

Table 2 provides properties of another exemplary embodiment of acopper-based alloy suitable for the present disclosure for use in asucker rod coupling or subcoupling.

TABLE 2 0.2% Offset Ultimate Elongation Charpy V- Yield Strength Tensileat Notch Impact (ksi) Strength (ksi) break (%) Energy (ft-lbs) Average161 169 6 N/A Minimum 150 160 3 N/A

The rod couplings of the present disclosure can be made using castingand/or molding techniques known in the art.

The couplings made of the spinodally-decomposed copper alloys uniquelyhave high tensile and fatigue strength in combination with high fracturetoughness, galling resistance, and corrosion resistance. The uniquecombination of properties allows the couplings to satisfy basicmechanical and corrosion characteristics needed while reliablyprotecting system components from galling damage, thereby greatlyextending the lifetime of the system and reducing the risk ofunanticipated failure.

Another type of artificial lift coupling is used in the drive shaft ofan artificial lift pump powered by a submersible electric motor that isdisposed in the well bore or is disposed outside of the well bore. Thecouplings are used to join segments of the pump drive shaft together andto join the drive shaft to the motor and to the pump impeller. Thesecouplings also include a keyway feature to assure a sound connectionbetween parts. The keyway feature can increase localized stress and is apotential origin source of a crack under torsional load, particularlywhen starting the motor. Such a failure can be mitigated by using thecopper alloys of the present disclosure, which have high strain ratefracture toughness.

The following examples are provided to illustrate the couplings,processes, and properties of the present disclosure. The examples aremerely illustrative and are not intended to limit the disclosure to thematerials, conditions, or process parameters set forth therein.

Examples

Two sucker rod couplings were made from a spinodally hardened copperalloy. The copper alloy was 15.1 wt % nickel, 8.2 wt % tin, 0.23 wt %manganese, and contained less than 0.05 wt % Nb, less than 0.02 wt % ofZn and Fe, and less than 0.01 wt % of Mg and Pb. The copper alloy had a0.2% offset yield strength of 102 ksi, and an ultimate tensile strengthof 112 ksi. The coupling had a nominal size of 1 inch according to APISpecification 11B. The threads were roll formed using a tap for theoperation. FIG. 11 is a picture of one end of the coupling.

Destructive testing was performed. A sample was sawed in half and thethreads were mounted and polished for analysis. A hardness test wasperformed at various locations on the part. FIG. 12 is a pictureindicating the measured values. The measured Vickers hardness (HV) isreported on top, and the Rockwell C hardness (HRC) is reported on thebottom (converted from the HV). As seen here, the HRC varied from a lowof 21.7 at the interior of the thread to a high of 38.7 at the outersurface of the thread. All of the HRC values on the outer surface of thethread were above 35. The average grain size was 23 microns. The grainswere elongated on the outer surface of the threads.

FIGS. 13-17 are various micrographs of the sample. FIG. 13 is amicrograph at 50× magnification showing the grain structure of theentire thread. FIG. 14 is a micrograph at 100× magnification showing thegrain structure of the tip of the thread. FIG. 15 is a micrograph at100× magnification showing the grain structure at the center of thethread. FIG. 16 is a micrograph at 100× magnification showing the grainstructure at the thread root. FIG. 17 is a micrograph at 200×magnification showing the grain structure at the side of the thread.

It will be appreciated that variants of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be combined intomany other different systems or applications. Various presentlyunforeseen or unanticipated alternatives, modifications, variations orimprovements therein may be subsequently made by those skilled in theart which are also intended to be encompassed by the following claims.

1-15. (canceled)
 16. A drilling component for use in oil and gasproduction comprising: a spinodally-hardened copper-nickel-tin alloyincluding from about 8 wt % to about 20 wt % nickel and from about 5 wt% to about 11 wt % tin.
 17. The drilling component according to claim16, wherein the drilling component includes a connector, a coupling, abushing, a bearing, a tubing, or combinations thereof.
 18. The drillingcomponent according to claim 17, wherein the drilling component is acoupling for a sucker rod.
 19. The drilling component according to claim17, wherein the drilling component is for use in hydrocarbon extraction.20. The drilling component according to claim 18, wherein thehydrocarbon extraction is performed at a temperature ranging from −193°F. to 572° F.
 21. The drilling component according to claim 16, whereinthe spinodally-hardened copper-nickel-tin alloy has a toughness asmeasured by Charpy V-notch impact energy of at least 22 ft-lbs at roomtemperature.
 22. The drilling component according to claim 16, whereinthe spinodally-hardened copper-nickel-tin alloy has a Yield Strength0.2% offset of at least 75 ksi and an Ultimate Tensile Strength of atleast 105 ksi.
 23. The drilling component according to claim 16, whereinthe spinodally-hardened copper-nickel-tin alloy has an Elongation atbreak of about 3% to about 18%.
 24. The drilling component according toclaim 16, wherein the spinodally-hardened copper-nickel-tin alloy has aHardness (HRC) of about 22 to about
 38. 25. The drilling componentaccording to claim 16, wherein the spinodally-hardened copper-nickel-tinalloy has a Hardness (HRB) of about 93 to about
 111. 26. The drillingcomponent according to claim 16, wherein the spinodally-hardenedcopper-nickel-tin alloy has a Yield Strength 0.2% offset of about 90 ksito about 150 ksi.
 27. The drilling component according to claim 16,wherein the spinodally-hardened copper-nickel-tin alloy has an UltimateTensile Strength of about 105 ksi to about 160 ksi.
 28. The drillingcomponent according to claim 16, wherein the spinodally-hardenedcopper-nickel-tin alloy includes from about 14.5 wt % to about 15.5 wt %nickel, and from about 7.5 wt % to about 8.5 wt % tin.
 29. The drillingcomponent according to claim 28, wherein the drilling component is acoupling and the coupling has a core including the spinodally-hardenedcopper-nickel-tin alloy, the core having a first end and a second end,each end containing an internal thread, wherein the internal threadshave a Hardness (HRC) of 22 to
 38. 30. The drilling component accordingto claim 28, the spinodally-hardened copper-nickel-tin alloy having: aYield Strength 0.2% offset of at least 90 ksi, an Ultimate TensileStrength of at least 105 ksi, and an Elongation at break of about 3% toabout 18%, and a Hardness (HRC) of about 22 to about
 38. 31. A rodstring comprising: a first rod and a second rod, each rod including anend with an external thread; and the drilling component of claim 16,wherein the drilling component is a coupling and the coupling has a coreincluding the spinodally-hardened copper-nickel-tin alloy, the corehaving a first end and a second end, each end containing an internalthread, the internal thread of the first end of the drilling componentcomplementary with the external thread of the first rod and the internalthread of the second end of the drilling component complementary withthe external thread of the second rod, wherein the internal threads havea Hardness (HRC) of at least about
 22. 32. The rod string according toclaim 31, the drilling component including spinodally-hardenedcopper-nickel-tin alloy including from about 14.5 wt % to about 15.5 wt% nickel, and from about 7.5 wt % to about 8.5 wt % tin.
 33. A pumpsystem comprising: a downhole pump; a power source for powering thedownhole pump; and a rod string located between the downhole pump andthe power source; wherein the rod string comprises: a first rod and asecond rod, each rod including an end with an external thread; thedrilling component of claim 16, wherein the drilling component is acoupling and the coupling has a core including the spinodally-hardenedcopper-nickel-tin alloy, the core having a first end and a second end,each end containing an internal thread, the internal thread of the firstend of the drilling component complementary with the external thread ofthe first rod and the internal thread of the second end of the drillingcomponent complementary with the external thread of the second rod,wherein the internal threads have a Hardness (HRC) of at least about 22.34. The pump system according to claim 33, the drilling componentincluding spinodally-hardened copper-nickel-tin alloy including fromabout 14.5 wt % to about 15.5 wt % nickel, and from about 7.5 wt % toabout 8.5 wt % tin.
 35. A drilling component for use in oil and gasindustry comprising: a spinodally-hardened copper-nickel-tin alloyconsisting of from about 8 wt % to about 20 wt % nickel, from about 5 wt% to about 11 wt % tin, and the remaining balance being copper, whereinthe alloy is substantially free of beryllium and lead.